聚（<em>N-</em>异丙基<em>丙烯</em>酰胺）立体异构体在水中的溶液行为：分子动力学模拟研究<a href="#fn1" title="可用电子补充信息（ESI）：第1节：链间径向分布函数。第2节：聚合物-聚合物氢键。第3节：LCST上方单链的线圈-小球过渡。残差联系人的时间演变：文件movie_m45_2_283K.avi，movie_m59_2_283K.avi，movie_m45_2_323K.avi和movie_m59_2_323K.avi。参见DOI：10.1039 / c7cp00808b">†</a>,Physical Chemistry Chemical Physics

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聚（N-异丙基丙烯酰胺）立体异构体在水中的溶液行为：分子动力学模拟研究 †
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2017-04-07 00:00:00 , DOI: 10.1039/c7cp00808b
G. Paradossi _{1,

2,

3,

4,

5} , E. Chiessi _{1,

2,

3,

4,

5}

Affiliation

聚（N-异丙基丙烯酰胺）PNIPAM的水亲和力受立构规整度调节，因为疏水性随全同立构规整度的增加而增加。在此实验证据的基础上，进行了PNIPAM立体异构体对在1.6％w / w聚合物水溶液（稀溶液和半稀溶液之间的中间条件）的原子分子动力学模拟，以比较研究无规立构的溶液行为和水合以及在较低的临界溶液温度LCST之上和之下的全同立构PNIPAM。30聚体，含内消旋二元组，m由于其立体化学组成与实验表征的PNIPAM立体异构体的立体化学组成相对应，因此假设伯努利亚二重分布的45％和59％的，被用作模型。在低于LCST的283 K处的模拟结果显示，立构规整度对链大小有轻微影响，但富内消旋二元体系的链间缔合倾向较高，与实验结果一致。链之间的连接是由于疏水相互作用而形成的，并由一层氢键合的水分子稳定，与同一个内消旋体相比，其迁移率降低了无限稀释的富含-dyad的立体异构体。在LCST上方的323 K，模拟检测到了线圈到小球的过渡以及链的聚集。在这些条件下，立构规整度对PNIPAM骨料特性的影响可以忽略不计。

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Solution behaviour of poly(N-isopropylacrylamide) stereoisomers in water: a molecular dynamics simulation study†

The water affinity of poly(N-isopropylacrylamide), PNIPAM, is tuned by tacticity, since the hydrophobicity rises with the increase of the degree of isotacticity. On the basis of this experimental evidence, atomistic molecular dynamics simulations of pairs of PNIPAM stereoisomers in 1.6% w/w polymer aqueous solution, a condition intermediate between the dilute and semidilute regimes, were carried out to comparatively investigate the solution behaviour and hydration of atactic and isotactic-rich PNIPAMs, both below and above the lower critical solution temperature, LCST. 30-mers with contents of meso dyads, m, of 45% and 59%, built assuming a Bernoullian dyad distribution, are used as models since their stereochemical composition corresponds to that of experimentally characterized PNIPAM stereoisomers. The simulation results at 283 K, below the LCST, show a slight influence of tacticity on the chain size, but a higher propensity for inter-chain association of the meso-dyad-rich system, in agreement with the experimental results. Junctions between chains are formed because of hydrophobic interactions and are stabilized by a layer of hydrogen bonded water molecules, whose mobility is reduced as compared to that observed for the same meso-dyad-rich stereoisomer at infinite dilution. At 323 K, above the LCST, simulations detect both the coil–globule transition and the aggregation of chains. Under these conditions, the influence of tacticity on the characteristics of PNIPAM aggregate is negligible.

更新日期：2017-04-07

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